| Chirality is ubiquitous in nature,including biological molecules such as DNA and proteins.This is due to the homochirality of its components(D-sugar and L-amino acids)and plays a pivotal role in the evolution of life.With the extensive research on chiral properties,researchers have gradually made a lot of discoveries in the fields of materials science,electrochemistry and biosensors,pharmaceuticals,catalysis and enantioselective separation.As a typical chiral material,chiral helical polymer has a helical structure similar to DNA.According to its different side groups,chiral materials with various properties can be obtained,which can meet various needs of people,so it has been widely concerned by people.Chiral helical substituted polyacetylene is one of the most widely studied chiral polymers.Its helical structure is dynamically adjustable and can produce many changes under external stimuli,so it has an important application prospect in the field of intelligent response materials.However,because the chiral helical substituted polyacetylene has a relatively rigid helical structure,its film forming property is poor,and it is difficult to obtain practical application.It is a very good way to introduce the helical substituted polyacetylene into the flexible elastomer film material by blending or chemical bonding.At the same time,the flexible elastomer film has the advantages of stretchability,wear resistance,weather resistance and biocompatibility.The chiral film materials obtained by combining the chiral helical substituted polyacetylene with flexible elastomer film materials have a very good application prospect.In order to achieve a wider application value,circularly polarized luminescence(CPL),as an important optical phenomenon,can be realized through chiral film materials,and CPL emission can be realized by adding fluorescent components to it.However,changing the CPL emission only by changing the helical structure of the chiral polymer through external stimulation can no longer meet the needs of people,and more efficient high-performance and dynamically adjustable CPL emission needs to be realized.Based on this,this dissertation introduced helical substituted polyacetylene into Polydimethylsiloxane(PDMS)through chemical bonding by casting into a film to achieve dynamic control of chirality/CPL under multiple stimuli.In addition,we introduced photochromic molecules into the chiral polyurethane film to achieve dynamic CPL control by regulating fluorescence.Based on the above chiral luminescence polyurethane film,we prepared a series of polyurethane systems that exhibit nonreciprocity when not doped with chiral helical substituted polyacetylene,and explored the mechanism of nonreciprocity.The main research contents of this dissertation are as follows:(1)A flexible stretchable photoluminescent PDMS film was prepared.This film consists of a chiral helical substituted polyacetylene with a double bond in the side group and hydrogenated silicone oil for hydrosilylation,and uses vinyl silicone oil as the base to obtain a chiral polyacetylene cross-linked flexible stretchable PDMS film.By adding fluorescent chromophore,CPL emission can be achieved under the excitation of excitation light.Adding chiral copolymers to PDMS can avoid the shortcomings of easy migration of chiral polymers in the polymer matrix.In addition,the addition of chiral polymer can solve the shortcomings of poor film-forming and non-heat resistance of chiral helical polyacetylene,and the polymer film can well protect the helical structure of the polymer,so that it can still achieve excellent CPL emission at high temperature.At the same time,because PDMS is easy to stretch,the dynamic adjustable CPL emission can be realized by tension-recovery test of the film.Because PDMS is responsive to low polar solvents and chiral polymers are responsive to polar solvents,the thin films can detect polar solvents and low polar solvents and achieve solvent polarity response.Based on the above experiments,the mechanism of CPL emission is clarified,and the chiral amplification is realized by stacking with pure PDMS film,and the theory of "reflection-reabsorption" is proposed.(2)A chiral luminescent polyurethane film with light response and acid-base response was prepared.Based on the principle that cyanostilbene(CS)is prone to Z/E isomerization under UV and acid-base stimulation,we first prepared a kind of CS alkyne monomer,which solved the disadvantage of its poor solubility.The UV light response and acid-base response of CS alkyne monomer in solution and thin film were measured respectively.The excitation wavelength dependence of CS alkyne monomer in solution is dependent,and the emission law is different in solution and thin film.The fluorescence is regulated by illumination and acid-base response,and then the CPL regulation of the response is realized.Secondly,a chiral light-emitting polymer was obtained by copolymerizing CS alkyne monomer and chiral alkyne monomer SA,and the light response was realized.Finally,a CS-Rh B fluorescent monomer was obtained by combining CS with rhodamine B(Rh B),which showed different fluorescence emission,fluorescence emission and CPL emission with UV light response and acid-base response at the same time.(3)A kind of photochromic polyurethane film was prepared,which showed very good photoresponse.A dihydroxyl spiropyran(SP)monomer was synthesized and SP was chemically bonded with polyurethane film.Under the irradiation of 365 nm UV light,the C-O bond of SP was broken into MC with open-loop structure,and changed back to SP under the condition of 254 nm UV light or heating,and had cyclability.Based on this,we added blue fluorescence chromophore ACA to the system to achieve blue CPL emission through selective absorption/transmission.With ACA as energy donor,red CPL emission is realized by energy transfer method.Finally,dual-band CPL emission is realized by two mechanisms.In addition,by adjusting the ratio of SP to fluorescent chromophore BPEA,CPL emission with adjustable colors among green,white and red is realized.Orange CPL emission is realized by complexing MC with metal ions,and finally full-color CPL emission is realized.Based on the photochromic phenomenon,the pattern design and multi-level anti-counterfeiting application are realized.(4)A series of nonreciprocal polyurethane films were prepared by casting method,and the mechanism of optical nonreciprocity was explained in detail for the first time.Six kinds of polyurethane films were obtained by the reaction of two oligomeric diols(polytetrahydrofuran(PTMG),polyethylene glycol(PEG))and three diisocyanates(HDI,MDI,TDI).Finally,six kinds of pure polyurethane films,six kinds of polyurethane films doped with achiral polyacetylene PY and six kinds of polyurethane films doped with chiral polyacetylene R/S-PFA were obtained.The rotation angles(every 45°)of the above 18 kinds of polyurethane films were tested on both sides.Finally,the nonreciprocal CPL emission is realized with the participation of blue fluorescent group ACA.FT-IR results show that there is hydrogen bonding between polyurethane and polyacetylene,which induces nonreciprocity of achiral polyacetylene.The optical properties and XRD characterization of the four kinds of polyurethane films were characterized.At the same time,combined with the optical information and XRD characterization of the above18 kinds of polyurethane films,the reason for the nonreciprocity of polyurethane film was obtained: there is a crystal-like structure in polyurethane film,and the rotation arrangement of the crystal-like structure produces nonreciprocity. |
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